Data from experimental animals and human epidemiological studies have suggested that hypohydration and/or low water intake is linked to poor glucose regulation and diabetes. The aim of this study is to investigate the effects of cellular dehydration on glucose in healthy non-diabetic individuals. METHODS: 60 males and females (30-55 y) will will undergo two experimental trials (ISO and HYP), consisting of a 2-h intravenous infusion of isotonic or hypertonic saline on two separate occasions, followed by a 4-h oral glucose tolerance test. Blood samples were taken from an antecubital vein in 30-min intervals starting at baseline for assessment of fluid and glucose regulating factors. Thirst will be assessed via visual analog following each blood sample. Energy substrate oxidation will be calculated via indirect calorimetry every 60 min.